1. Field of the Invention
The present invention relates to engine timing apparatus for measuring the timing advance/retard angle of a multi-cylinder internal combustion engine.
2. Description of the Prior Art
For many years, it has been conventional practice in providing for the measurement and adjustment of the ignition advance angle of an internal combustion engine to provide a visible timing mark on the pulley of the engine. A stroboscopic lamp or "timing light" is directed on the pulley to illuminate the timing mark. The timing light is energized under the control of ignition pulses from the ignition system, so that the timing mark appears to be stationary when illuminated by the timing light. By adjusting the delay interposed between an ignition pulse from the ignition system and the subsequent firing of the timing light so that the timing mark appears to be at a top dead center position, it is possible to determine the amount of ignition timing advance with respect to top dead center.
In prior art engine timing apparatus, the time delay between firing of the cylinder (typically the No. 1 cylinder) and the flashing of the timing light typically has been adjusted by means of a potentiometer which has a calibrated knob or dial. When the proper setting of the potentiometer has been attained, the dial on the potentiometer is read by the operator. This gives an indication of the degrees of advance of the No. 1 ignition pulse with respect to top dead center. An example of this type of prior art engine timing apparatus is shown in U.S. Pat. No. 3,597,677 by R. S. MaC Crea and Joseph C. Marino.
U.S. Pat. No. 3,955,135 by Fastaia shows another engine timing apparatus in which a delay potentiometer is adjusted by the operator. Timing is measured by enabling a digital counter to measure the time between the firings of the No. 1 cylinder (as measured by a No. 1 cylinder probe) and a delayed output signal from the timing light. The timing advance angle is computed based upon the count representing the time delay, the number of cylinders of the engine, and the contents of a counter used to compute rpm of the engine. The computed timing advance is displayed on an output display unit.
The prior art engine timing apparatus has typically required not only the timing light, but also a No. 1 probe for sensing when the No. 1 ignition pulse is produced and a probe or connector to produce a signal indicating firing of each of the cylinders of the engine. Often the service technician is merely interested in a quick check of timing, and the connecting of several connectors or probes is an inconvenience to the technician. There is a continuing need for improved engine timing apparatus using a timing light which is easier for the technician to use, and which requires a minimum number of probes or connectors in order to perform the timing function.
With the advent of low cost electronic devices, and in particular microprocessors, digital electronic systems have found increasing use in a wide variety of applications. Digital electronic systems have many significant advantages over analog systems, including increased ability to analyze and store data, higher accuracy, greater flexibility in design and application, and the ability to interface with computers having larger and more sophisticated data processing and storage capabilities. There is also a continuing need in engine analyzer systems for an engine timing apparatus which is consistent with and takes full advantage of the capabilities of microprocessors and digital circuitry to control the timing light and the engine timing function.